Preparation and Characterization of Itraconazole- or Miconazole-Loaded PLGA Microspheres

The purpose of this study was to prepare poly(lactide-co-glycolide) (PLGA) microspheres (MS) loaded with itraconazole (ITCZ) or miconazole (MCZ) under different evaporation temperatures (25 or 40°C) using an oil-in-water emulsion solvent evaporation method in order to evaluate the initial burst release of drug. Loading efficiencies were comparatively good and the diameters of prepared drug-loaded PLGA MS were around 20 µm in all formulations. The release rates of ITCZ-PLGA MS prepared at 40°C showed a significantly restricted release profile compared with the corresponding ITCZ-PLGA MS prepared at 25°C. This difference in release rate of ITCZ was thought to be caused by the self-healing effect of PLGA, as the glass transition temperature of PLGA is around 40°C. With respect to the MCZ-PLGA MS, the initial burst release was similar in formulations prepared at both 25 and 40°C. Scanning electron microscope results suggested that the initial burst release was due to the localization of MCZ on the surface of MCZ-PLGA MS at higher concentrations. Differential scanning calorimetry measurements suggested complete amorphization of MCZ in MCZ-PLGA MS, whereas crystalline ITCZ was detected in the ITCZ-PLGA MS. This complete amorphization of MCZ is considered to be one of the reasons for the initial burst release.